In the related art, there is a known laser microscope provided with a photomultiplier tube (PMT) serving as a detector that detects light and outputs an intensity signal of the detected light (for example, see Patent Literature 1). A PMT has a risk of suffering degradation when an excessive level of light is incident thereon, and therefore, in a conventional laser microscope, the maximum range of the intensity signal from the PMT which can be converted to brightness information (hereinafter referred to as “full scale”) is set to a range that does not cause degradation of the PMT, and the laser light power, a high-voltage (HV) applied to the PMT, or the like is adjusted so that the output signal from the PMT does not exceed the full scale.